There are two ways I use to make a herb infused oil, fast and slow
Traditional way: Slow, low energy and very effective at making a well rounded oil.
Fill a glass jar with fresh or dried herbs, rosemary is best if cut up a bit with scissors, and cover with oil such as olive or almond or grapeseed, even corn or veg works though. Keep it in a dark place and let infuse 3-6 weeks. Strain. Store in a cool, dark place or the fridge. Basically just fill the jar with herbs and then pour enough oil to cover the herbs.
The jar can be infused on a sunny windowsill (solar infused oil) however, the solar method since essential oils are destroyed by sunlight it's not suitable for all herbs, it can help to evaporate off some of the moisture of very wet herbs but you lose something of the essence of the herb oils too.
Fresh herbs are highly recommended, but good herb infused oils can be made out of good dried herbs as well. Again, chop up the dried stuff before infusing so that the essential oils and other herbal properties can be more easily absorbed by the oil.
Fastest method:
Over low heat, warm the oil and the roughly chopped herbs for 1-3 hours until the oil is well infused by the herb's essences.
Be sure to watch carefully, don't allow this mixture to simmer or boil or burn the herbs, as this heat will destroy vitamins and change the basic oil's properties as well as making the finished oil taste burnt.
Jars are better than bottles for making the infused oils since it's easier to get the herbs out afterwards to strain through a very fine sieve or muslin.
Pour the finished oil into a bottle with a sprig or two of fresh rosemary before storing......it's a nice gift too.
Excellent on home made bread fresh from the oven to be eaten with pasta or cheese sauce covered veggies
Himself likes it drizzled over salads.
cheers,
Toddy